The present invention relates to electric motors which have an electronic commutation and more particularly relates to the structure thereof.
As is known, motors having an electronic commutation comprise, among other elements, a housing which contains a wound armature from which a shaft extends. The commutation means of this armature, instead of being formed by an electromechanical device consisting of a ring and brushes, are in this case formed by an electronic device having a control module.
This type of motors usually presents a delicate problem of manufacture, construction and assembly. Indeed, windings must be formed and disposed in slots of the armature, then the ends of the wires of the winding coils of this armature must be connected to the electronic circuit of the control module and, lastly, it must be possible to dissipate the heat of the power components of the electronic circuit of the control module.
One difficulty relates to the forming of the windings of the armature when it is desired to proceed automatically and the slots of the armature do not permit prefabricating these windings in such a way as to merely place them in the slots. In such a case, in particular if it is desired to proceed mechanically or automatically, there must be used a winding machine provided with an articulated arm which rotates about an axis and is supplied with wire from a reel taking the wire from a reserve supply. This arm describes a relatively complex path in order to form the wire, as it is unwound, into loops which are placed in succession in the slots. To operate in this way, it is therefore necessary to so arrange the armature that it is relatively free from obstructions and provides ease of access in order to avoid hindering the travel of the rotating articulated arm, in particular by the presence of contactors which will receive the ends of the wires or conductors of each coil.
One difficulty is presented by the connection of the ends of the wires of the coils with the electronic circuit of the control module, which is usually achieved by soldering the wire ends to terminal connectors associated with the electronic circuit. Most of the time, bearing in mind the configuration of the structure of the motor, such a soldering can only be carried out manually. In relatively conventional motors having a star connection, many solderings must be carried out since the winding coils of the armature are multiple and each coil requires two solders. Such an operation, which is particularly difficult to automate, therefore requires very great skill and is time-consuming. It must be remembered that, for this operation, the ends of the wires are then without any material support and are as it were "in the open" or "in the air", which renders this operation particularly delicate, especially as it must be carried out in a very limited space difficult of access. Further, whatever the dexterity of the operator, the solders are subject to faulty contacts. For example, these solders may be "dry", i.e. the scavenging solution of the soldering flux in fact insulates the wire from the terminal connector instead of ensuring electrical continuity.
In order to overcome another difficulty, there is often employed for the electronic device an insulating substrate which carries a conductive printed circuit on which the components of the electronic circuit of the control module are placed, fixed and connected. After having been thus equipped, this substrate is usually placed in proximity to one of the end walls or bells of the housing of the motor and preferably in the vicinity of the inner side thereof. However, as this circuit comprises power components which must be cooled so as to avoid the heating thereof which would otherwise have a destructive effect, an arrangement is adopted in which the insulating substrate is provided with throughway orifices, and the power components are directly fixed to the end wall of the motor, through these orifices; in this way this end wall, owing to its mass and its metallic nature, acts as a radiator evacuating the heat produced in the power components in operation of the motor. The fact of having to divide the electronic circuit, in such manner that some of its components are no longer on the substrate itself but mounted directly on an end wall, requires additional operations for placing in position, fixing and then electrically connecting, by soldering, these components to the printed circuit of the substrate; it will be easily understood that this also complicates the mounting and assembly operations and may also result in defective workmanship.
A technique for overcoming some of the previously-mentioned difficulties is for example disclosed in the document FR 89-11 771 filed on Sep. 8, 1989 in the name of the applicant. However, the technique disclosed does not permit carrying out a winding, a connection and then an assembly which are automatic.